Embodiments of the invention relate generally to an optical imaging system and more particularly to an optical imaging system having the capability of changing to multiple focal lengths with polarization light.
Inspection devices including borescopes, videoscopes, fiberscopes, and endoscopes are non-destructive evaluation (NDE) tools widely used in industrial applications and medical applications. The inspection devices are often used to inspect inaccessible locations for damage or wear or to verify whether parts have been properly manufactured or assembled. The inspection devices may employ an external light source coupled to fiber optic bundles or a light source, such as light-emitting diode (LED), placed at the device's distal end to provide illumination of a target. When the target is illuminated, an image of the target is formed by a lens system on an image sensor, and the image is relayed to a display such as a video screen. In order to inspect a large range of field, the lens system in front of the image sensor with a fixed focal length needs to be designed to achieve a large depth of field (DOF). However, a larger DOF lens will result in a darker image due to the smaller aperture stop used. Such darker images may result in inspection failures or difficulties. Typically, a set of a variety DOF tips with different lenses are used in inspection devices with some tips offering near field inspection and the other tips being used for mid to far field inspection. However, repeatedly changing the tips is time-consuming and may decrease the inspection efficiency and user convenience.
Therefore, it is desirable to provide an inspection device and method of operating the inspection device to address the above-mentioned problems.